Midkiff K, Harris D, Gilsenan A, Kellier-Steele N, McSorley D, Andrews EB. Results of a long-term postmarketing case series of adult osteosarcoma and teriparatide in the United States. Poster presented at the 35th ICPE International Conference on Pharmacoepidemiology & Therapeutic Risk Management; August 27, 2019. Philadelphia, PA. [abstract] Pharmacoepidemiol Drug Saf. 2019 Aug 20; 28(S2):688. doi: 10.1002/pds.4864

BACKGROUND: The Osteosarcoma Surveillance Study was initiated at the time of approval of Forteo in the United States (US) to monitor for a potential association between teriparatide (an osteoporosis treatment) and osteosarcoma (OS). OS occurs at a background incidence rate of approximately 2.5 cases per million per year in US adults aged 40 years or older.

OBJECTIVES: To provide final study results, including descriptive characteristics of adult patients with OS.

METHODS: Incident cases of OS diagnosed between January 1, 2003, and December 31, 2016, were identified through participating cancer registries in the US. Information on prior exposure to medications and possible risk factors was obtained via self-report (or proxy-report) telephone interview. Exposure information was verified through medical record abstraction for a sample of patients. A standardized incidence ratio was estimated to compare the observed to expected number of OS cases with a prior history of teriparatide treatment. The expected number of exposed OS cases was the product of the background incidence rate of OS standardized to the age and sex distribution of teriparatide-treated patients, the person-years at risk following first exposure to teriparatide, and the percentage of cases that were interviewed.

RESULTS: Interviews were completed for 24% (1,173) of patients diagnosed with OS between 2003 and 2016; three reports of teriparatide use prior to diagnosis were identified. Based on the background incidence rate, the expected number of OS cases among patients treated with teriparatide was 4.17. Given the three observed cases, the standardized incidence ratio was 0.72 (90% CI, 0.20-1.86). Demographic characteristics were similar for interviewed and noninterviewed patients, and agreement was 92% or higher between self-reported and chart-recorded osteoporosis medication exposure information. Mean age of interviewed patients was 61 years, 53% were male, and 84% were white. The prevalence of known risk factors for development of OS among the OS cohort was 19% for history of radiation and 4% for history of Paget’s disease of bone.

CONCLUSIONS: This study found that the incidence of OS associated with teriparatide use during the 15-year surveillance period was no different than that which would be expected based on the background incidence rate of OS.

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